Classification of Epithelial Tissue Flashcards

Classification of Epithelial Tissue

• Epithelial tissues are classified based on the number of layers (simple or stratified) and cell shape (squamous, cuboidal, columnar).

Simple Epithelium

• Consists of a single layer of cells, facilitating absorption, secretion, and filtration.
• Found in organs like kidneys, alveoli, and capillaries where diffusion is prioritized.

Simple Squamous Epithelium

• Cells are flattened and thin, allowing rapid diffusion.
• Cytoplasm is sparse, enhancing permeability.
• Locations include kidneys, lungs, lining of the heart, and blood vessels (endothelium).

Endothelium and Mesothelium

• Endothelium: Lines blood vessels and heart, part of simple squamous epithelium.
• Mesothelium: Covers serous membranes in the ventral cavity, also part of simple squamous epithelium.

Simple Cuboidal Epithelium

• Comprises a single layer of box-like cells with round nuclei.
• Functions primarily in secretion and absorption.
• Forms walls of small ducts and kidney tubules, and covers ovary surfaces.

Simple Columnar Epithelium

• Made of tall, closely packed cells, promoting absorption and secretion.
• Ciliated type aids in moving mucus; non-ciliated type lines the digestive tract.

Pseudostratified Columnar Epithelium

• Appears stratified due to cell height variation but is a single layer.
• Functions in secretion and absorption; can be ciliated (found in the trachea) or non-ciliated (in male reproductive ducts).

Stratified Epithelia

• Composed of two or more cell layers, providing durability and protection against wear.
• Basal cells continuously regenerate to maintain the layer.

Stratified Squamous Epithelium

• Most common stratified type, resistant to abrasion.
• Found in places subjected to friction, such as the esophagus, mouth, vagina, and skin.

Stratified Cuboidal Epithelium

• Rare type, typically two cell layers thick.
• Found in sweat and mammary glands.

Stratified Columnar Epithelium

• Limited distribution; exists in specific regions like the pharynx and male urethra.
• Transitional areas between different epithelium types often contain this layer.

Transitional Epithelium

• Unique structure allows for stretching as organs like the bladder fill.
• Basal cells are typically cuboidal or columnar; apical cells change shape based on the organ’s state.
• Locations include the ureters, bladder, and parts of the urethra.